In recent years, conditions in uses have become hard with an expansion in uses of polymeric materials, whereby, various properties required for the polymeric materials are becoming more severe. In some uses, since the polymeric materials are exposed to high temperatures and strength is lowered by softening, there is caused a problem of being incapable of using.
Epoxy resin compositions have been employed in a variety of fields such as laminating, coating, adhesion, encapsulating, molding, etc. However, because of the above-mentioned reasons, properties required have not become sufficiently satisfied in an epoxy resin composition in which a bisphenol A epoxy resin is employed which is usually employed at present.
In order to improve heat resistance, although there is tried the use of a multi-functional type epoxy resin such as a novolak type multifunctional epoxy resin, a three-functional epoxy resin and a four-functional epoxy resin, mechanical strength at high temperatures is not sufficient, and there is a drawback that a cured product obtained from the multi-functional type epoxy resin is hard, but brittle.